Field of the Invention
The present invention relates to an image processing method and apparatus and, more particularly, to image processing of reading out, by an imaging medium, additional information from a printed product in which information other than image information, for example, voice information, text information, and completely different image information such as pieces of information about an image are visually unnoticeably embedded as additional information in the image information.
Description of the Related Art
Conventionally, extensive studies have been made on multiplexing information associated with an image on image information. Recently, a technique called a digital watermark technique has been standardized, which multiplexes additional information such as an author name and user permission/inhibition on the image information of a photograph, a painting, or the like such that the additional information is difficult to visually discriminate, and distributes the image information via a network such as the Internet. As another application field, there is a technique of embedding additional information in an image in order to specify an output device and its device number from an image output on paper, in order to prevent forgery of a paper money, stamp, securities, and the like along with the improvement of the image qualities of image output apparatuses such as a copying machine and printer. For example, Japanese Patent No. 3959890 proposes a technique of, when embedding a digital watermark in a printed product, embedding a pattern whose color or brightness is changed in accordance with the type or properties of the printed product in an arbitrary type of digital watermark method, thereby making the pattern unnoticeable.
In Japanese Patent No. 3959890, there are a plurality of different information adding methods, and the pattern is embedded in the printed product by one of the methods. In this case, if a multiplexing method such as the digital watermark technique that is invisible to a user is used, the user cannot know a decoding method to be used for processing to acquire the information from the printed product, and needs time to try the methods one by one.